Bones or portions of bones often comprise an outer relatively hard layer referred to as cortical bone and inner material referred to as cancellous bone. A variety of physical conditions can cause cancellous bone to become diseased or weakened. Such conditions can include, for example, osteoporosis, avascular necrosis, cancer or trauma. Weakened cancellous bone can result in an increased risk of fracture of the cortical bone surrounding the cancellous bone, because the diseased or weakened cancellous bone provides less support to the exterior cortical bone than healthy cancellous bone.
One common condition that is caused by diseased or damaged cancellous bone is vertebral compression fractures. A vertebral compression fracture is a crushing or collapsing injury to one or more vertebrae. One of the leading causes, but not an exclusive cause, of vertebral compression fractures is osteoporosis. Osteoporosis reduces bone density, thereby weakening bones and predisposing them to fracture. The osteoporosis-weakened vertebrae can collapse during normal activity and are also more vulnerable to injury from shock or other forces acting on the spine. In severe cases of osteoporosis, actions as simple as bending can be enough to cause a vertebral compression fracture.
While the vertebral compression fractures may heal without intervention, the crushed bone may fail to heal adequately. Moreover, if the bones are allowed to heal on their own, the spine may be deformed to the extent the vertebrae were compressed by the fracture. Spinal deformity may lead to other adverse conditions, such as, breathing and gastrointestinal complications, and adverse physical effect on adjacent vertebrae.
Minimally invasive surgical techniques for treating vertebral compression fractures are becoming more and more common. One such technique used to treat vertebral compression fractures is injection of bone filler material into the fractured vertebral body. This procedure is commonly referred to as percutaneous vertebroplasty. More specifically, vertebroplasty involves inserting an inject needle into bone material in the vertebra and injecting bone filler material (for example, bone cement, allograph material or autograph material) into the collapsed vertebra to stabilize and strengthen the crushed bone.
Another type of treatment for vertebral compression fractures is known as Kyphoplasty. Kyphoplasty is a modified vertebroplasty treatment that uses one or two balloons, introduced into the vertebra. First a cannula or other device is inserted into the vertebra. The cannula may have one or more balloons associated with it or another device may be inserted with balloons. As the balloons are inflated, the balloons push the cancellous bone outwardly, crushing or compacting the cancellous bone to create a cavity, which significantly alters the natural structure of the cancellous bone. The balloons are then deflated and removed, leaving a cavity. Bone cement is injected into the cavity to stabilize the fracture.